SBRT Treatment Planning: Practical Considerations

For single isocenter dose
distributions, the dose fall-off
from prescription isodose to
half of the prescription dose
typically occurs over the
shortest distance if the dose
is prescribed to the 80%
isodose shell, with 100% as
maximum dose.
If 100% is PD, then 125%
should be the maximum dose
to have sharpest ratio of
R 50% (Ratio of 50%
Prescription isodose volume
to the PTV volume)
Sanford L. Meeks et al Int. J. Radia. Onc. Biol. Phys., Vol. 41, No. 1, pp. 183–197, 1998